So, after doing the Spartan training with this general, who starts at 16 in the campaign and is notable for having a bodyguard of militia hoplites (that is also notable for always pushing him to the back of the stack, but that's a minor inconvenience), I decided to join him up with my main forces to besiege the settlement at West of Thessalonike. After spending a turn on the stack, I noticed something rather unusual: he wasn't on the stack anymore, and by the side of the stack, there was a new general. Selecting him, you would see that there were no units cards under his command at all, not even his own. You could move him around, attach him to stacks (including full ones), and check his stats by right clicking, but selecting him now to move or anything else is a real chore, and I am afraid something else might be broken.